Feeding and management of older horses: Part 2 (Animal Science Update)
This is the second of a series of articles in my column on feeding and managing the older horse. If you missed the last one, we covered when an older horse is considered geriatric and what we can do about weigh loss.
In this column we will focus on older horses with other conditions that would lead to a change in diet like poor dentition, pituitary or thyroid problems and inadequate kidney or liver function.
Horse’s teeth grow continuously throughout their lives and frequently form sharp points on the outside of the upper molars and inside of the lower molars. These points make it painful to chew and cause the horse to dribble feed or partially chewed boluses of hay from its mouth (“quidding”).
The teeth of horses fed dry hay and grain need more frequent attention than those on lush pasture. Tooth loss, especially molars or premolars, also reduces the ability to adequately prehend and chew feed. If an upper molar is lost, the opposing teeth will grow down into the space (wave mouth), making it difficult to chew. Inadequate dentition predisposes the horse to weight loss and/or choke.
Older horses, especially those known to have missing molars, should have their teeth checked at least twice a year. If chewing is difficult, pelleted or extruded feeds can be made into watered down mashes for easier consumption.
Only “complete” pelleted feeds which are designed to be fed without hay should be used since many pelleted feeds are only grain substitutes and do not contain the proper amounts of fiber and mineral balance to be used as the major or sole source of nutrition for the horse. Enough water should be added to the pellets to make a soupy consistency to prevent choke.
Hay can still be fed if choke is not a problem, even if most of it is wasted. Access to good pasture is desirable. However, if front incisors are missing (as in cribbers) or badly aligned, do not rely on pasture as a source of nutrition. These horses must be fed complete feeds or loose hay and/or hay cubes since they cannot graze effectively.
Thyroid tumors usually are benign but can increase the incidence of obesity and subsequent metabolic conditions like founder.
These tumors can cause glucose intolerance, in which the horse becomes less sensitive to the action of insulin. After a high sugar or starch meal blood levels of both glucose and insulin become abnormally high, resulting in increased thirst and urination.
If properly managed, horses with these tumors can live for years after appearance of the clinical signs. Since plasma levels of vitamin C are reduced in aged horses with pituitary tumors, 5 to 10 grams of ascorbic acid in the feed per day may be beneficial. If water intake and urine output are increased, fresh, clean water should be available free choice.
If chronic founder is a problem, the horse’s access to fresh grass and grain must be restricted (properly fitted muzzles work best) and sudden dietary changes avoided. If the horse has a thick hair coat it should be clipped in the summer, in addition to providing shelter from the sun to keep the horse comfortable on hot summer days.
Chronic kidney or liver failure is not as common in aged horses as it is in cats and dogs, but still can occur. The degeneration of the kidney and liver ability to function is progressive and irreversible but can be slowed and the clinical signs managed to a degree with diet.
Reduced kidney function will result in renal stones (calculi), bladder stones, weight loss, loss of appetite, and potentially death. Horses are unique in that they excrete excess dietary calcium through their urine instead of their feces as do other animals.
As a result, if kidney function is reduced, renal and bladder “stones” of calcium oxalate are more likely to occur as well as an increase (potentially lethal) in blood calcium.
Horses with kidney failure should be put on low calcium diets (less than 0.45-percent calcium on a dry matter basis). Good quality grass hay or a complete pelleted ration for mature horses (10-percent protein) are the feeds of choice. Avoid legumes (alfalfa and clover), wheat bran, and beet pulp due to high calcium (legumes, beet pulp) or phosphorus (wheat bran) content.
Liver failure results in weight loss, lethargy, jaundice, loss of appetite, and intolerance of fat and protein in the diet. If severe, the horse may show behavioral changes such as irritability, aimless wandering or circling, or pressing its head against objects.
Affected horses require increased sugar/starch sources to maintain their blood glucose levels and are intolerant of high protein or fat in the diet. Legumes should not be fed due to the high protein content.
The diet should emphasize starch intake (grains or concentrates); however, fiber sources (hay, beet pulp) are still necessary to avoid gastrointestinal dysfunction.
Grass hay, low protein sweet feeds or grains like corn and milo are recommended components of the ration to keep the protein content down and starch level up. Wheat bran and beet pulp are acceptable supplements in these cases. Since the liver is the site of B-vitamin (especially niacin) and vitamin C synthesis in the horse, daily oral supplementation with B-complex and ascorbic acid may be beneficial.
A horse should not be treated differently just because it has reached a certain chronological age.
However, if problems related to aging are present, changes in management and medications may be needed to keep the older horse comfortable.
This material has been updated from an archived Rutgers NJAES FactSheet by Dr. Sarah Ralston, “Management of Older Horses” (https://njaes.rutgers.edu/pubs/publication.php?pid=FS715). Have a great early spring and think warm!